Abstract. Organic compounds play a central role in troposphere chemistry and
increasingly are a viable target for remote sensing observations. In
this paper, infra-red spectral features of three organic compounds
are investigated in thermal emission spectra recorded on a flight
on 8 May 1998 near Aire sur l'Adour by a
balloon-borne instrument, MIPAS-B2, operating at high spectral
resolution. It is demonstrated, for the first time, that PAN and
acetone can be detected in infra-red remote sensing spectra of the
upper troposphere; detection results are presented at tangent
altitudes of 10.4 km and 7.5 km (not acetone). In addition, the results
provide the first observation of spectral features of formic acid in
thermal emission, as opposed to solar occultation, and confirm that
concentrations of this gas are measurable in the mid-latitude upper
troposphere, given accurate spectroscopic data. For PAN, two bands
are observed centred at 794 cm−1 and 1163 cm−1. For acetone and
formic acid, one band has been detected for each so far with band
centres at 1218 cm−1 and 1105 cm−1 respectively. Mixing ratios
inferred at 10.4 km tangent altitude are 180 pptv and 530 pptv for
PAN and acetone respectively, and 200 pptv for formic acid with
HITRAN 2000 spectroscopy. Accuracies are on the order of 15 to
40%. The detection technique applied here is verified by examining
weak but known signatures of CFC-12 and HCFC-22 in the same spectral
regions as those of the organic compounds, with results confirming
the quality of both the instrument and the radiative transfer model.
The results suggest the possibility of global sensing of the organic
compounds studied here which would be a major step forward in
verifying and interpreting global tropospheric model calculations.